Using an OSC broadcast, you can trigger your devices to play or stop at the same time, with a single command. This technique also extends to any other commands available via OSC, like setting live effect parameters on multiple devices at the same time, or changing the slide index, and so on.
All you need to do is set your OSC output IP address to your network's broadcast address. On most networks, you can find this address by simply replacing the last number of your device's IP address with "255". For example, if your Lightform device's IP address is 192.168.1.123, then your network's broadcast address is likely 192.168.1.255.
Here is an example of this in TouchOSC:

Once set, commands that you issue will be received by all of your Lightform devices on the network, rather than just a specific one.
Other things to note: